Particle decay in false vacuum

We revisit the problem of decay of a metastable vacuum induced by the presence of a particle. For the bosons of the `master field' the problem is solved in any number of dimensions in terms of the spontaneous decay rate of the false vacuum, while for a fermion we find a closed expression for the decay rate in (1+1) dimensions. It is shown that in the (1+1) dimensional case an infrared problem of one-loop correction to the decay rate of a boson is resolved due to a cancellation between soft modes of the field. We also find the boson decay rate in the `sine-Gordon staircase' model in the limits of strong and weak coupling.Comment: 19 pages, 2 figure

Metastable anisotropy orientation of nematic quantum Hall fluids

We analyze the experimental observation of metastable anisotropy resistance orientation at half filled quantum Hall fluids by means of a model of a quantum nematic liquid in an explicit symmetry breaking potential. We interpret the observed ``rotation'' of the anisotropy axis as a process of nucleation of nematic domains and compute the nucleation rate within this model. By comparing with experiment, we are able to predict the critical radius of nematic bubbles, $R_c\sim 2.6 \mu m$. Each domain contains about $10^4$ electrons.Comment: 10 pages, 8 figures, final version as will appear in PR

Degenerate Domain Wall Solutions in Supersymmetric Theories

A family of degenerate domain wall configurations, partially preserving supersymmetry, is discussed in a generalized Wess-Zumino model with two scalar superfields. We establish some general features inherent to the models with continuously degenerate domain walls. For instance, for purely real trajectories additional "integrals of motion" exist. The solution for the profile of the scalar fields for any wall belonging to the family is found in quadratures for arbitrary ratio of the coupling constants. For a special value of this ratio the solution family is obtained explicitly in terms of elementary functions. We also discuss the threshold amplitudes for multiparticle production generated by these solutions. New unexpected nullifications of the threshold amplitudes are found.Comment: 21 pages, LaTeX, 3 figures using epsf.st

New bounds on the neutrino magnetic moment from the plasma induced neutrino chirality flip in a supernova

The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account, in a more consistent way than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the neutrino spin-flip. The best upper bound on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to 7.Comment: 19 pages, LaTeX, 7 EPS figures, submitted to Journal of Cosmology and Astroparticle Physic

Neutrino electromagnetic properties and new bounds on neutrino magnetic moments

We give a brief outline of possible neutrino electromagnetic characteristics, which can indicate new physics beyond the Standard Model. Special emphasis is put on recent theoretical development in searches for neutrino magnetic moments.Comment: 4 pages, to appear in J. Phys.: Conf. Ser. (2012), based on the talk presented at the XII International Conference on Topics in Astroparticle and Underground Physics (TAUP 2011), Munich 5-9 September 201

Heavy ion collisions: Correlations and Fluctuations in particle production

Correlations and fluctuations (the latter are directly related to the 2-particle correlations) is one of the important directions in analysis of heavy ion collisions. At the current stage of RHIC exploration, when the details matter, basically any physics question is addressed with help of correlation techniques. In this talk I start with a general introduction to the correlation and fluctuation formalism and discuss weak and strong sides of different type of observables. In more detail, I discuss the two-particle $p_t$ correlations/\mpt fluctuations. In spite of not observing any dramatic changes in the event-by-event fluctuations with energy, which would indicate a possible phase transition, such correlations measurements remain an interesting and important subject, bringing valuable information. Lastly, I show how radial flow can generate characteristic azimuthal, transverse momentum and rapidity correlations, which could qualitatively explain many of recently observed phenomena in nuclear collisions.Comment: 8 pages, 8 figures. Invited talk at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, February 8-12, 2005, Salt Lake City, Kolkata, Indi

Dirac-Neutrino Magnetic Moment and the Dynamics of a Supernova Explosion

The double conversion of the neutrino helicity $\nu_L \to \nu_R \to \nu_L$ has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range $10^{-13} \mu_{\rm B} < \mu_\nu < 10^{-12} \mu_{\rm B}$ and a magnetic field of $\sim 10^{13}$ G between the neutrinosphere and the shock-stagnation region, an additional energy of about $10^{51}$ erg, which is sufficient for a supernova explosion, can be injected into this region during a typical shock-stagnation time.Comment: 10 pages, LaTeX, 4 EPS figures, accepted to JETP Letter

Estimates with an Effective Chiral Lagrangian for Heavy Mesons

On the basis of an effective lagrangian incorporating approximate chiral symmetry and heavy-quark spin and flavor symmetries, and by use of information on leptonic decays, we estimate the effective $D^\star D\pi$ coupling.Comment: UGVA-DPT 1992/07-779, BARI-TH/92-117 Revised version, September 1992, LaTeX (style article), 7 page